Browsing by Author "Dietel, Thomas"

Now showing 1 - 9 of 9
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    A feasibility study for electron-muon correlations at ALICE
    (2025) Nathanson, Nina; Dietel, Thomas; Buthelezi, Zinhle; Fortsch, Siegfried
    A Feasibility Study for Electron-Muon Correlations at ALICE Nina Nathanson, February 2024 This analysis aims to assess the feasibility of using e-μ pairs as an alternative dilepton probe for heavy quark studies in proton-proton collisions. The e-μ channel would provide a much cleaner/low background signal than other currently-utilized probing methods, but it is statistics-limited, a re-striction which is of increased concern at ALICE due to the detector's geometry. With the use of Pythia simulations, the viability of undertaking an analysis of the channel using ALICE p-p data from LHC Run 3 is considered. The analysis finds that it is feasible to undertake a data study of the e-μ pairs and presents an estimate of the expected signal in a year of Run 3 data.
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    Calibrating and recommissioning the ALICE transition radiation detector
    (2023) Barrella, Jason; Dietel, Thomas
    Starting from the year 2022, the LHC produces a factor 6 increase in the interaction rate of Pb-Pb collisions from 8 to 50 kHz, offering exciting new avenues of research in the field of heavy-ion physics. Changes to the ALICE experiment include the introduction of an entirely new software framework as well as an approximate 100 fold increase in statistics and significant improvements in tracking capabilities which will further expand the realm of potential research. The work presented here consists of three primary parts. Firstly, in preparation for new detector control systems at CERN, core software for the ALICE Transition Radiation Detector was updated and migrated to a new version control system. Pipelines were also developed to automatically deploy packages to remote repositories. Secondly, drift velocity and $E times B$ calibration software was developed and tested on Run 2 data. A mean angular resolution of 2.6$^circ$ was achieved. This was found to be within a range of a previous result that could be plausibly explained by a number of factors. Finally, components were written in the new ALICE O$^2$ software framework with applications in calibration, TRD geometry transformations, and a new TRD event display. All were tested successfully and the event display was deployed to the new TRD web page.
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    Charged Vector Boson (W ±) production in simulated proton-proton collisions at √s = 5.36 TeV.
    (2025) Potgieter, Jakobus; Buthelezi, Zinhle; Fortsch, Siegfried; Dietel, Thomas
    In this work, the focus is on the charged vector boson (W ±) production in the forward rapidity region of simulated relativistic proton-proton collisions, where the POWHEG and Pythia Monte Carlo (MC) event generators are used to simulate the events of interest for the analysis. The W ± boson production is studied via the muonic decay channel as W ± → μ±+νμ (–). It is theoretically motivated in the work that this process can serve as a probe of the initial state of the collision, since the W ± boson is produced in the hardest partonic interaction and neither the W ± boson nor the μ± have a colour charge. The muonic decay of heavy-flavour (HF) mesons in the same forward rapidity region is also investigated, where it is shown that these processes serve as the dominant background for the muon production from W ± boson decays. The primary charged-particle multiplicity is also introduced as an observable of interest, where the self-normalised W ± boson production as a function of the normalised multiplicity is defined and studied specifically. For this observable, it is shown that a linear trend is obtained when estimating the multiplicity in the central rapidity region and using the default Monash Tune. The choice of the central region for the multiplicity estimation is clearly motivated by looking at auto-correlation effects - which are shown to effect the slope of the multiplicity observable. In addition, it is shown that the slope of the multiplicity observable is also sensitive to the multi-parton interaction (MPI) and colour reconnection (CR) models - which motivates the use of the observable to probe the initial-state of the collision. Finally, a feasibility study is also performed to investigate whether the same study can be done with the ALICE Run 3 proton-proton reference data at the same centre-of-mass energy - where an estimation of the available statistics for the W ± → μ±+νμ (–) process is presented. Through the work, it is also argued that the study in proton-proton collisions can serve as a meaningful baseline measurements for other collision systems - such as proton-lead and lead-lead.
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    Common Mode Effect of the ALICE Transition Radiation Detector - Baseline Shift
    (2021) Elimam, Ali; Dietel, Thomas
    The Transition Radiation Detector is a sub-detector of the ALICE experiment that is used primarily as an electron detector and a trigger mechanism. The TRD currently has 521 individual chambers distributed over 18 super modules. Each chamber houses a radiator, a drift region and a multi-wire proportional chamber with the readout electronics. When charge is absorbed in the anode wires of the multi-wire proportional chamber, it creates a common-mode effect, this common-mode effect manifests itself as a drop in the signal produced by the surrounding readout electronics where no particle has traversed, called the baseline. Capacitors have been installed in a layout to produce a low-pass filter (RC circuit) to decrease the impact of the common-mode effect. These capacitors were installed for a pad row pair, creating capacitor coupling for a high voltage supply segment. However, these capacitors were prone to failure, causing dead chambers that could not be used to acquire data for the remainder of the run, so it was decided to remove them. With their removal, the extent of the common-mode effect on the baseline had to be understood and corrected for in order to better calibrate the detector system. The University of Cape Town has one chamber, an L3C0 chamber. This chamber was used to collect two datasets with the same parameters, one with the 2.2 nF capacitors installed and the other without the 2.2 nF capacitors, to study the effect. It is found that the drop in baseline is only experienced by anode wires with the same capacitor coupling. Furthermore, it is observed that there is a linear relationship between the charge absorbed by the anode wires and the drop in baseline, thus charge absorbed by the anode wires can be summed should they have the same capacitor coupling. It is also found that the drop in baseline is 2.5 times larger in the dataset without capacitors. The final part of the thesis corrects for this common-mode effect, using a correction factor determined from the dataset
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    Designing an event display for the Transition Radiation Detector in ALICE
    (2021) Perumal, Sameshan; Dietel, Thomas; Kuttel, Michelle
    We document here a successful design study for an event display focused on the Transition Radiation Detector (TRD) within A Large Ion Collider Experiment (ALICE) at the European Organisation for Nuclear Research (CERN). Reviews of the fields of particle physics and visualisation are presented to motivate formally designing this display for two different audiences. We formulate a methodology, based on successful design studies in similar fields, that involves experimental physicists in the design process as domain experts. An iterative approach incorporating in-person interviews is used to define a series of visual components applying best practices from literature. Interactive event display prototypes are evaluated with potential users, and refined using elicited feedback. The primary artefact is a portable, functional, effective, validated event display – a series of case studies evaluate its use by both scientists and the general public. We further document use cases for, and hindrances preventing, the adoption of event displays, and propose novel data visualisations of experimental particle physics data. We also define a flexible intermediate JSON data format suitable for web-based displays, and a generic task to convert historical data to this format. This collection of artefacts can guide the design of future event displays. Our work makes the case for a greater use of high quality data visualisation in particle physics, across a broad spectrum of possible users, and provides a framework for the ongoing development of web-based event displays of TRD data.
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    Machine learning approaches towards tuning ALICE TRD simulations
    (2024) Ramraj, Nikhiel; Dietel, Thomas
    In this work an exploration of the discrepancies existing between real and simulated data pertaining to the ALICE Transition Radiation Detector is carried out as a motivation to tune the necessary parameters in the ALICE Online-Offline simulation software (O2 ). After such exploration a single parameter namely the Xe gas gain is subjected to modification. A machine learning approach is taken with the use of deep learning discrimination mechanisms namely artificial neural networks and convolutional neural networks to quantify the effect that our tuning has on the improvement of the simulation results and their conformation to the real data. The correspondence of the optimal values suggested by deep learning approaches is investigated with pulse height spectrometry. It is shown that the optimal parameters suggested by our deep learning models through inference of their performance metrics are not clear and in agreement with that suggested by naive pulse height inspections.
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    Machine learning for particle identification & deep generative models towards fast simulations for the Alice Transition Radiation Detector at CERN
    (2019) Viljoen, Christiaan Gerhardus; Dietel, Thomas
    This Masters thesis outlines the application of machine learning techniques, predominantly deep learning techniques, towards certain aspects of particle physics. Its two main aims: particle identification and high energy physics detector simulations are pertinent to research avenues pursued by physicists working with the ALICE (A Large Ion Collider Experiment) Transition Radiation Detector (TRD), within the Large Hadron Collider (LHC) at CERN (The European Organization for Nuclear Research).
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    Measurement of Neutral Mesons in p-Pb collisions at √sNN = 8.16TeV with the ALICE detector
    (2019) Ahmed, Samah; Dietel, Thomas
    The measured transverse momentum spectra of neutral pion π 0 and η mesons are presented for p-Pb collisions at √ sNN = 8.16 TeV using the photon conversion method for the signal extraction. This method uses the tracking and particle identification capabilities of the central barrel detectors of ALICE. Signal extracted down to 0.3 GeV/c and 0.7 GeV/c for π 0 and η respectively. The resulting spectra are presented and systematic uncertainties have been evaluated. A suppression of the yield compared to pp collisions at the same center of mass energy is observed in RpA for both mesons. Comparisons to theory predictions show consistency with the spectra and RpA.
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    Performance of a photon conversion trigger in proton-proton collisions using the ALICE Transition Radiation Detector
    (2022) Barreiros, Andre S; Dietel, Thomas
    The study aimed to find the yield of conversion photons in pp √ s = 13 TeV with less uncertainty for high transverse momentum photons through the TRD in ALICE (necessary for π 0 and η cross-sections). The calculation of the yield of conversion photons were successful in replicating their yield from minimum bias data set. During this process it was detected that the TRD trigger formed a smaller data set within the minimum bias than was hoped for, leading to high uncertainties. To remedy the trigger efficiency uncertainties, a Monte Carlo simulation of LHC18o, LHC18k2, was proposed to supplement the lack of statistics in the data. The TRD trigger was replicated within the MC data set, allowing for the comparison of relative cut efficiencies between the two data sets. This enabled the further identification of discrepancies between the data set, limiting its use for the TRD. The various discrepancies detected were: i) differences in the sagitta values of the TRD tracks; ii) particles from photon conversions are about 10% more likely to find a corresponding TRD track in MC; iii) HQU (Quarkonium) trigger cuts had varying relative efficiency for conversion photons between data sets; iv) the deflections of TRD tracklets differed by about 0.176 mm. Discrepancy ii) can be halved by limiting pile-up photons. Charged particles with pT > 2 GeV/c from the primary vertex are well simulated within the TRD. In relation to point iv). the difference in deflection seems to be too small to affect TRD trigger efficiency and should be remedied. The MC seems to have the most problems in simulating late conversion, low transverse momentum tracks. As a result, conversion photons are not well simulated in the MC.